Quantitative analysis of nobiletin in shiikuwasa (Citrus depressa Hayata) juice

概要

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Shiikuwasa (<I>Citrus depressa</I> Hayata) is cultivated in the northern areas of the Okinawa main island, Japan. Whole shiikuwasas were extracted for juice processing using extractors. The polymethoxylated flavone nobiletin is a characteristic component of shiikuwasa, and its various biological activities have been extensively reported. In this study, nobiletin concentration in shiikuwasa juice samples was quantitatively determined by high-performance liquid chromatography (HPLC), and the change in nobiletin concentration in shiikuwasa juice during processing was analyzed. Shiikuwasa juice was concentrated with a centrifugal evaporator, and some extraction solvents were examined by HPLC. The optimum extraction solvent was found to be methanol. Nobiletin concentration was determined to be 0.1mg/100g, with a coefficient of variation of 1.8%. A juice sample extracted from only the edible part of the fruit contained a very low nobiletin concentration (0.2mg/100g). Therefore, it was suggested that nobiletin in juice extracted from whole shiikuwasas is from peel tissues. Also, it was indicated that centrifugation during juice processing markedly affects nobiletin concentration in shiikuwasa juice.